Bumping PHP to supported version from 8.0 to 8.2 + dependencies

[escopecz]

I can see this warning in the CI that has now started to fail:

You are running PHP CS Fixer on PHP 8.3.29, but the minimum PHP version supported by your project in composer.json is PHP 8.0. Executing PHP CS Fixer on newer PHP versions may introduce syntax or features not yet available in PHP 8.0, which could cause issues under that version. It is recommended to run PHP CS Fixer on PHP 8.0, to fit your project specifics.

That highlights 2 issues. One is that this library is still supporting a version that is 2 years out of security updates. We should upgrade that to 8.2 which still gets security updates:

https://www.php.net/supported-versions.php

While messing with dev dependencies I increased versions for CS fixer (that allowed me to see and automatically fix the issues from the CI), PHPSTAN and added Rector with default config. Plus adding a step for CI to run it.

[patrykgruszka]

Isn't this a BC? I think we should update the requirements in README.md and bump the major version of this lib.

Rest of the changes are looking good.

[escopecz]

Yes, we are planning to release V4 as requested in #316 (comment) as the v4-beta is released for a year now. It's a good opportunity to update. I updated Readme.

[RCheesley]

Looks good to go from my side, readme comment is clear. Thanks @escopecz!